Do you know altitude sickness begins to appear at (aproximately) what altitude?

8000 feet but:: 8000 ft is often when people notice significant symptoms yet at 5000 ft many are breathless ; those who are very susceptible may complain of headache or occasional nausea. More serious high altitude pulmonary edema or high altitude cerebral edema emerge at higher altitude but it is speed of ascent rather than absolute height which increases risk. Danger very high at or above 11, 500 ft.